MEMPHIS, TN, USA - Three of the Top 4 seeds reached the semifinals of the Regions Morgan Keegan Championships & the Cellular South Cup on Thursday, with Sabine Lisicki the only exception, defeating No.3 seed Lucie Safarova in the only upset.

Lisicki, the sixth seed, won a battle of big-hitting baseliners as she took on Safarova, firing nine aces and breaking serve four times for a 63 64 win over the Czech lefty in the pair's first ever meeting.

"It was a very close match where every point was so important," Lisicki said. "I served really well and on the big points I really went for my shots. I've been seeing how all of the Top 10 and Top 20 players play and I'm learning from it."

Lisicki will have another first meeting in the semifinals on Friday, as she faces Victoria Azarenka. The No.2 seed downed No.8 seed Pauline Parmentier, 64 62.

"I wasn't as aggressive as I needed to be early on, but I changed my game in time," Azarenka said. "I hope to play better in my next match. I think I'm getting better with each match; I'm getting more comfortable with the courts."

"It was my first tournament of the year because I've been injured, so it's a good visit to the States for me," said Parmentier, who hurt her right wrist just before the Australian season and was out until this week. "I played very good this week, winning two matches and playing well today. I'm happy."

The other semifinal will see Caroline Wozniacki and Anne Keothavong play for the first time. Top seed Wozniacki ended the run of qualifier Michaella Krajicek, 26 63 63, while fourth seed Keothavong edged fifth seed Marina Erakovic, 62 16 62.

"Michaella was playing really well and didn't really let me play the game I wanted to play, but I'm just happy to be through," Wozniacki said. "She was serving well, so when I broke her the first time it gave me confidence to keep going forward. This is my first time in the semifinals of Memphis so hopefully it'll go well."

"I definitely lost a little bit of focus in that second set, but I got it back for the third set; but walking off the court with the win is really what you need," said Keothavong about her match with Erakovic. "I'm feeling good about my tennis right now. At this time last year I was playing on the ITF Circuit, and my ranking was a lot lower. I'm moving in the right direction."

Both singles semifinals, as well as the second doubles semifinal, will take the court on Friday, with both finals scheduled for Saturday at the indoor event.